How should flexible and stretchable structures be tested for reliability?

Written by Sanna Lahokallio

4 April 2019

Application such as wearable and medical electronics and flexible displays have unique structures compared to traditional electronics – they tend to implement novel flexible and stretchable structures and materials. These structures enable completely new and interesting products, but reliability and functionality testing-wise there are some obstacles. Many of these products are used in demanding environments or in applications related to safety of the user. Consequently, new test methods designed for these structures are needed to ensure their reliability.

We are currently developing a tester called FlexStress Dynamic, which combines dynamic mechanical stresses with environmental stresses. The development is funded by European Regional Development Fund (ERDF). The tester enables combinatory testing of flexible and stretchable structures by combining mechanical stress with environmental conditions such as high temperature and humidity.

Why do we want to build a tester which combines mechanical and environmental stresses? Because in real life conditions products are facing both of these factors simulatenously. If a structure is bended at laboratory environment, it behaves differently than when it is bended in humid conditions. Therefore, bending testing without environmental exposure may give much too optimistic results and thereby not reveal important reliability issues. This is vitally important, especially, when the reliability of new polymer-based structures is tested. Polymers are widely used in flexible and stretchable applications and they may be very vulnerable to conditions combining mechanical and environmental stressors.

We are not planning to expand our business to building testers, but we wanted to build the tester to be able to help our customers by offering test methods specified for the needs of flexible and stretchable structures. Currently we are testing our smaller tester and building another tester which can be used inside a humidity chamber. Service for FlexStress Dynamic will be available during this spring! Sanna, Laura and the small tester are going to travel to IDTechEx Show exhibition held in Berlin on April 10-11. Please come to meet us and the tester to talk more about your testing needs!

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